Very high-frequency emitting radar antennas have been used in the detection of land mines or other concealed objects. As used herein, the term ‘very high frequency’ refers to radar systems employing at least some frequency components in a range in excess of 30 MHz. Moreover, while radar systems, and the invention described herein, may advantageously be employed for a wide variety of non-intrusive inspection (NII) applications, including, without limitation, narcotics detection, bomb detection, buried cable and pipe detection, motion detection, corpse detection, see-through-the wall technology, archaeology, geophysics, etc., the invention is described, herein, in terms of a ground-penetrating radar (GPR) system for the detection of landmines, with no intent of limitation.
In certain applications, such as those of GPR, proximity of the emitting antenna to the ground is known to be beneficial (particularly, proximity on the order of 30 centimeters or less) by virtue of reducing radar footprint on the ground and thereby improving the intensity of the signal that is reflected by the buried object. However, when the antenna is located near the ground or other objects, undesired reflections may appear between the antenna and the ground or other objects. Multiple reflections result in interference referred to as “clutter”. These multiple reflections are primarily a function of the following: distance between the antenna and the ground, the presence of other objects in the vicinity of the antenna, roughness of the terrain, the angle of the antenna, and the radar reflectivity of the antenna and its components. These multiple reflections interfere and mask the reflected signatures of the buried objects and are referred to as ‘clutter’. It is extremely beneficial to have system components that minimize this clutter.